Grid shows Hour Angle (HA) using your longitude and the selected time.
Advanced settings
3D Planetarium Controls
Drag mouse to rotate the sky
Scroll wheel to zoom in/out (auto-adjusts magnitude to show fainter stars when zoomed in)
Click a star/planet for info
Right-click magnitude slider for custom values
Touch: swipe with one finger to rotate the sky
Touch: pinch with two fingers to zoom in/out
Touch: tap a star/planet for info
Touch: use the ☰ button to show/hide these controls
Touch: press and hold the magnitude slider for custom values
Phone: tap 🧭 and hold your phone up to the sky - the map follows where the back of the phone points. Tap Align and centre a bright object in the camera to correct the compass; align on a second object for the best accuracy. Pinch still zooms; dragging hands control back to your finger
Adjust magnitude filter to show/hide faint stars
Toggle "Auto-adjust magnitude on zoom" to link zoom level with star visibility
Set your latitude/longitude for local sky orientation
Toggle stars/planets visibility
Toggle horizon grid (altitude/azimuth with N/E/S/W)
Toggle equatorial grid (HA/DEC: Hour Angle and Declination)
Toggle the ecliptic line
Toggle constellation figures for the 24 most prominent constellations, with optional names. The line data comes from d3-celestial and every vertex has been snapped onto a star in this catalogue, so the figures meet the stars they are drawn from
Toggle star names to label named objects - 407 stars carrying an official IAU proper name, plus the named clusters, nebulae and galaxies in this catalogue. Search accepts those names too (try "Mizar", "Algol" or "Andromeda Galaxy")
Search finds names in every language the map offers and forgives small typos ("Betelguese" finds Betelgeuse). Suggestions appear as you type: pick one with the arrow keys and Enter, or click it. Catalogue numbers (HD, NGC, IC, M) must be exact, so "M13" never turns into M31
Tick "Unknown magnitude" to show catalogue objects that have no recorded V-Mag (drawn in blue); they are excluded from the magnitude slider because there is no honest value to compare against
Tick "Render stats" for a readout of how many objects the last frame drew and how long it took
Reset view to default orientation and zoom
Use the Time control to preview the sky at any date/time; the grid labels show Hour Angle (HA).
Tip: Focus the Time box and press Arrow Up/Down to adjust with rollover. Move the caret over year/month/day/hour/minute to change that unit. If caret isn't available, use Shift (hour), Ctrl (day), Alt (month), or Ctrl+Shift (year).
Set Magnitude Limit:
Align on a bright object
Pick one you can see. You'll centre it in the camera, which corrects the compass. Aligning on a second object, well away from the first, fixes all three axes.